Good ventilation is absolutely essential to the proper functioning of any roofing system. Improper ventilation is one of the most common problems we find in roofs, and can lead to all sorts of negative consequences, from mold growth to wrinkles in the underlayment.

Condensation

We're all familiar with condensation forming on the windows when it's cold outside and warm inside. Pretty much the same thing can happen in an improperly vented attic when the home's heating system is cranked up in cold weather.

Wrinkles

One of the most obvious ways condensation can destroy your roof is by wrinkling the underlayment felt, a frighteningly swift process that can occur in a single night with the right conditions and is not the fault of any contractor. Wrinkled felt transforms a shingle roof into an eyesore - and the really bad news is, it's often irreparable. Felt can easily wrinkle to the extent that the entire roof has to be replaced.

Mold

Mold requires four components to grow: A food source (pretty much any organic material such as wood), a relatively dark location, a warm environment, and moisture. Your attic provides at least the first three of these elements, and there's not much you can do about it. The last element, moisture, is the key - and one of the main reasons why proper attic ventilation is so important. Poor ventilation leads to condensation, which leads directly to mold, which often leads to serious health hazards for people living in the home. Mold is also almost impossible to remove from wood; if there's a bad infestation, the entire roof deck may have to be replaced. That's a pretty high price tag compared to a few roof vents.

Compromising of Insulation

The kind of insulation you find in attics is designed to be effective when dry. If it gets wet, it sags, sticks together, stops trapping any air, and generally becomes useless as insulation - with predictable consequences for your utility bill.

Energy Consumption

On a typical 90 degree day, the surface of a standard roof can easily reach almost twice that temperature. Most of that heat is transmitted directly into the attic space through convection, bringing the temperature inside the attic to about 165 degrees. This hot air is going to look for a way out. It will first attempt to go up, but if it finds no openings in the roof deck, it will take the next available option - down, into the house, where it is cooled by the air conditioning system.

You may never notice a "blast of hot air" from the attic, but you will likely notice the utility bill at the end of the month, which may reflect an air conditioning system running much more than necessary. Adequate ventilation in the roof, even in the form of just a few inexpensive vents, can save you hundreds of dollars in cooling costs over a summer.